Comments (3)

1. 

   WANG Runying - November 24th, 2011 at 17 h 32 min

   Developing countries need in particular technologies with low-tech concept, low-cost and easy installation and maintenance, high performance, and eco-friendly ship for their household water treatment. Phytopurification such as constructed wetlands will be an effective solution.

2. 

   Bilal Khan - November 24th, 2011 at 17 h 53 min

   Wang, we at the world water forum secretariat agree with you. You are one of the first persons who talked about low cost technologies for developing countries. Apart Phytopurification, can you please give us another example? Thanks.

3. 

   BITRA SADA SIVA - December 23rd, 2011 at 12 h 06 min

    
   We, as a Non-Governmental Development organisation wokring towards bringing significant changes among poor communities in rural, urban, coastal and tribal areas for poverty reduction and self reliance. We are wokring with this model in different parts of backward areas in India.
   We are promoting Bio-sand filters in the villages, which works in the same way as traditional slow sand filters, which have been used for centuries. The difference is that the biosand filter is smaller, and water does not need to flow through it all the time. The filter can be built anywhere in the world because it uses materials that are locally available. The filter itself is simply a concrete or plastic container, with layers of sand and gravel inside. The sand and gravel remove sediment, pathogens, and other impurities from the water. This is absolutely a low cost technology.

   Contaminated water is poured into the top of the filter whenever it is needed. There is a diffuser plate placed just above the sand bed that absorbs the shock of the falling water so it does not disturb the sand. The water slowly passes through the biolayer, sand and gravel. Filtered water flows out the tube and is collected by the user in a storage container. The storage container is placed on a block or stand so that the opening is just under the spout.

   How does it remove contaminants?

   As with all slow sand filters, a biological layer (often called a biolayer) of sediment and microorganisms develops at the sand surface. Pathogens and suspended material are removed from contaminated water through a combination of biological and physical processes in the biolayer and sand bed. These processes include:

   ·         Mechanical trapping

   ·         Predation

   ·         Adsorption/Attraction

   ·         Natural death

   For further details, one can visit http://www.dhan.org/vayalagam/biosand_filters.php